There are existing apparatus which can be used to sharpen a cutting blade of a rotary shaver; such as, U.S. Pat. No. 2,953,851 which issued to Wheeler in 1960 and U.S. Pat. No. 3,932,967 which issued to Hanes in 1976. Both of these patents disclose abrasive annular rings which are intended for insertion between a disc form rotary cutting blade and a comb-like circular shaving head of a rotary shaver.
There are a number of disadvantages with using abrasive annular rings. One disadvantage is that the annular rings must be specially adapted for use with a particular model of rotary shaver. Another disadvantage is that the annular rings are relatively fragile and are prone to being torn or bent by a misaligned blade. A final disadvantage relates to difficulties in installation as the shaving head or the annular ring can be damaged when installing the annular rings in position within the shaving head.